Is there anything to stop the core devs saying we want unlimited bitcoin and changing the code to allow it. I mean, 21 million isn't much. 
And why you want it? Perhaps you don't fully understand what made bitcoin, bitcoin.There is a lot of factors that many of us go crazy with bitcoin and one of these is the limited supply that leads to it being scarce. And I think everyone had already explained some factors and don't need to explain further.
Maybe you try to hack the system.
In the past Bitcoin was hacked and the hackers, maybe hacker made a lot of Bitcoins. It is not done again but we all know that it is hard since that years and no one had been able to hack again is a proof it is hard. 21 million is enough, though not accurately 21 since there are a lot of of them lost in the void and some forgotten.
Can you support it? Seriously I just heard it like hackers hack the system and create more bitcoin, really? And even there is some bitcoin that is unrecoverable because of lost private keys, these are still belong in the 21 million supply.In the past Bitcoin was hacked and the hackers, maybe hacker made a lot of Bitcoins. It is not done again but we all know that it is hard since that years and no one had been able to hack again is a proof it is hard. 21 million is enough, though not accurately 21 since there are a lot of of them lost in the void and some forgotten.